It's the height of allergy season -- a particularly nasty one in some places -- and millions of sufferers have no easy escape from the airborne assault

Spring was suddenly in the air, a little later than usual, and trees were tardily emerging from their long winter dormancy, budding and flowering with vigor. Arboreal petals opened, exposing pollen-covered anthers to the breezes, which wafted pollen grains into the air, carrying some of them for many miles. By June, while the late-blooming trees were still in blossom, flowering grasses began contributing to the airborne assault, and many regions in the East began reporting record pollen counts.

As nature intended, the sheer number of pollen grains -- the botanical bearers of sperm -- ensured that at least some would reach...